Multimeter having communications via measurement terminals and communication system for same

ABSTRACT

A multimeter having measurement terminals and configured to receive measurement signals applied to the measurement terminals and a measurement value and also configured to receive communication signals applied to the measurement terminals and extract encoded information from the communication signals. The multimeter can be included in a multimeter communication system having a device coupled to the measurement terminals of the multimeter. The device is configured to generate communication signals having encoded information and provide the communication signals to the measurement terminals of the multimeter.

TECHNICAL FIELD

This invention generally relates to multimeters, and more particularly,multimeters communicating with external devices through the measurementterminals of the multimeter.

BACKGROUND OF THE INVENTION

There have been many approaches taken in providing electroniccommunications with a multimeter. One such approach is including adedicated communication ports and supporting circuitry in the multimeterfor the purpose of communicating with another device. For example, thesemultimeters have terminals for GPIB (general purpose instrument bus),USB (universal serial bus) or LAN (local area network) interface. A userconnects the appropriate connector to the communication terminal on themultimeter and the other device to allow communication between the two.Another approach to providing communications with a multimeter is toinclude a wireless interface and supporting circuitry that are used forcommunications. For example, these multimeters include infrared or radiofrequency communication interfaces. Communication between the multimeterand the device can occur when the two are placed within range of oneanother.

Although the previously described approaches provide the multimeter withthe ability to communicate with external devices, there areconsiderations to be made. In the case of including dedicatedcommunication ports in the multimeter, there are additionalmanufacturing costs involved with building such a multimeter. Anotherconsideration is compromising durability of the multimeter and itsresistance to the elements because the port represents another physicalelement of the multimeter that can fail and the opening can exposeinternal components of the multimeter to the elements. As for includingwireless communication interfaces, there are added costs associated withmaterials and manufacturing. Moreover, battery life for a multimeter canbe decreased due to the added power consumption from communicatingthrough a wireless interface.

Therefore, there is a need for an alternative solution to communicatingwith a multimeter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing of a handheld multimeter.

FIG. 2 is simplified block diagram of a multimeter communication systemaccording to an embodiment of the invention.

FIG. 3 is a simplified block diagram of a portion of the multimeter ofFIG. 2 according to an embodiment of the invention.

FIGS. 4 a and 4 b are flow diagrams for communicating in the multimetercommunication system according to embodiments of the invention.

FIGS. 5 a-5 d are simplified block diagrams of multimeter communicationsystems according to embodiments of the invention.

FIG. 6 is a simplified block diagram of a measurement probe andmultimeter communication system according to an embodiment of theinvention.

FIG. 7 is a simplified block diagram of a portion of the measurementprobe of FIG. 6 according to an embodiment of the invention.

FIG. 8 is a flow diagram for communicating in a measurement probe andmultimeter communication system according to an embodiment of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Certain details are set forth below to provide a sufficientunderstanding of embodiments of the invention. However, it will be clearto one skilled in the art that embodiments of the invention may bepracticed without these particular details. Moreover, the particularembodiments of the present invention described herein are provided byway of example and should not be used to limit the scope of theinvention to these particular embodiments. In other instances,well-known circuits, control signals, timing protocols, and softwareoperations have not been shown in detail in order to avoid unnecessarilyobscuring the invention.

FIG. 1 illustrates a multimeter 10 having a key pad 18 is provided forentry of information to the multimeter. The multimeter 10 furtherincludes a function selector 20 that allows an operator to choosevarious meter functions, for example, selecting a measurement functionof the multimeter 10. A display 22 is included for providing visualinformation to an operator, such as a measurement value. The multimeterfurther includes measurement terminals 12 to which test leads (notillustrated) connect for coupling the measurement terminals 12 to adevice under test. For example, a pair of test leads coupled to themeasurement terminals can be used to measure a voltage by coupling thevoltage to the measurement terminals though the test leads. Themultimeter measures the voltage coupled to the measurement terminals anddisplays the measured value on the display 22.

FIG. 2 illustrates a multimeter communication system according to anembodiment of the present invention. A device communicating with themultimeter (“DCMM”) 30 is coupled to measurement terminals 12 of themultimeter 10. As will be described in more detail below, the DCMM 30and the multimeter 10 can communicate information with each other by wayof communication signals provided through the measurement terminals 12.In contrast to conventional multimeter communication systems, themultimeter 10 does not communicate with the DCMM 30 through a dedicatedcommunication port. In one embodiment, the communication signalsrepresent digitally encoded information. Although FIG. 2 illustrates apair of measurement terminals 12 through which communications occur,other embodiments of the invention include a greater or fewer number ofmeasurement terminals through which communications can occur. Thus, itwill be appreciated by those ordinarily skilled in the art the scope ofthe invention is not limited by the specific number of measurementterminals of a particular embodiment.

FIG. 3 illustrates a portion of the multimeter 10 according to anembodiment of the present invention. The measurement terminals 12 arecoupled to an input circuit and A/D converter 50 that receives signalsapplied to the measurement terminals 12. The input circuit and A/Dconverter 50 can include protection circuitry that prevents damage tocomponents of the multimeter 10 that may occur when signals are appliedto the measurement terminals 12, such as when high voltage and/or highcurrent signals are accidentally applied during measurement ofelectrical characteristics. The input circuit and A/D converter 50 alsogenerates a digital representation of the analog measurement signalpresented at the measurement terminals 12. A processor 52 receives thedigital output of the converter 50 for processing and calculates ameasurement value. A memory 54, representing non-volatile and/orvolatile memory, is coupled to the processor 52 to store digitalinformation accessible by the processor 52. The processor 52 alsoreceives input from keypad 18 as well as from function selector 20,which are operative to control various functions of the multimeter.Processor 52 supplies data to alert output module 56 for generating analert signal, for example, an audible tone, during operation. Theprocessor 52 further supplies display data to display 22 in order toprovide visual readout of measurement values and times. Power supply 58including battery 60 supplies power to the various circuits of themultimeter 10. In operation, the multimeter 10 performs measurements ona programmed, cyclical basis, periodically sampling measurement signalsat the measurement terminals and converting them from analog to digitalform for processing and display.

The multimeter 10 of FIG. 3 further includes an input/outputcommunication circuit 64 coupled to the input circuit and A/D converter50 to receive signals applied to the measurement terminals 12. The I/Ocommunication circuit 64 detects input communication signals applied tothe terminals 12 by a DCMM (FIG. 2) and generates corresponding internalcommunication signals provided to a communication component 68 alsocoupled to the processor 52. The I/O communication circuit 64 furtherreceives internal communication signals from the communication component68 and generates output communication signals transmitted through themeasurement terminal 12 to a DCMM. The communication component 68extracts the information from the internal communication signals andgenerates internal control signals to carry out the desired actionaccording to the extracted information. For example, in one embodimentthe communication component 68 generates internal control signalsprovided to the processor 52, which in turn configures operation of themultimeter 10 according to the information extracted from the internalcommunication (i.e., input communication) signals.

In some embodiments of the invention, the information is digitallyencoded on the communication signals, and the multimeter 10 and the DCMM30 are configured to encode and decode the information. Conventionaldigital encoding and decoded schemes known to those in the art may beutilized in some embodiments of the invention. Additionally,conventional communication protocols known to those ordinarily skilledin the art can be utilized in some embodiments of the invention.

Although FIG. 3 illustrates the previously described blocks separately,in some embodiments, the different blocks can be combined together or ablock can perform the functions described for another block. In oneembodiment of the invention, an application specific integrated circuitcan include multiple ones of the blocks previously described. Forexample, the processor 52 and memory 54 can be included in an ASIC. Inanother example, an ASIC includes the processor 52, memory 54, and thecommunication component 68. In another embodiment, the I/O communicationcircuit 64 takes advantage of existing circuits in the input circuit 50.For example, the I/O communication circuit 64 utilizes processorcontrolled current sources, clamp circuit and the like, that are alreadypresent in the input circuit and A/D 50. Additionally, although thecommunication component 68 is shown in FIG. 3 as a separate block, insome embodiments, however, the role of the communication component 68 isperformed by the processor 52. For example, the processor can beoperable to extract information from the communication signals andgenerate appropriate internal control signals to perform desired actionsaccording to the communication signal. Additionally, the previouslydescribed blocks may be implemented using hardware, software, or acombination of the two.

FIG. 4 a illustrates a communication process 80 according to anembodiment of the present invention for communicating with themultimeter 10. At step 82, the multimeter 10 transmits a query signalthrough the measurement terminals 12 (FIG. 3) to indicate it is readyfor communication. A DCMM 30 coupled to the measurement terminals 12detects the query signal at step 83 and is notified the multimeter 10 isready for communication. In some embodiments, the query signal is adigital signal representing a binary code recognizable by the DCMM 30(FIG. 2). In other embodiments, the query signal is a signal alternatingat a specific frequency or having a known amplitude or magnitudedetectable by the DCMM 30. Other types of encoding may be used for thequery signal as well and the invention is not limited to the particularexamples previously described.

As will be described in more detail below, when the DCMM 30 communicatesinformation to the multimeter 10, the DCMM 30 transmits communicationsignals representing the information to the multimeter 10 by way of themeasurement terminals 12 at step 84. The multimeter 10, ready forcommunication since the transmission of the query signal, receives thecommunication signals at step 85 and extracts the information from thecommunication signals at step 86. Following the extraction ofinformation, the multimeter 10 performs the desired action according tothe extracted information at step 87.

In some embodiments, the multimeter 10 is set into a communication modeto establish communications between the DCMM 30 and the multimeter 10.In some embodiments, the multimeter 10 is set in the communication modeby user input through the keypad 18 or function selector 20. In otherembodiments, the multimeter 10 is set into the communication mode inresponse to receiving an initial communication signals from a DCMMcoupled to the measurement terminals 12. In other embodiments, themultimeter 10 is set into the communication mode upon switching on themultimeter, that is, the multimeter 10 is ready for communication assoon as it is switched on. The examples described are not intended tolimit the scope of the invention to the particular embodiments.

FIG. 4 b illustrates a communication process 90 according to anembodiment of the present invention for the multimeter 10 to communicatewith the DCMM 30. At step 92, the multimeter 10 generates communicationsignals having information to be provided to the DCMM 30. At step 93 themultimeter 10 transmits the communication signals having the informationto the DCMM 30 by way of the measurement terminals 12. The DCMM 30receives the communication signals at step 94 and extracts theinformation from the communication signals at step 96.

In one embodiment, the DCMM 30 represents a multimeter test system 100,as shown in FIG. 5 a, coupled to the measurement terminals 12 of themultimeter 10 for testing its functionality and operability. Forexample, after establishing communication between the test system 100and the multimeter 10, a test voltage signal having a known voltage canbe applied by the test system 100 to the measurement terminals 12 of themultimeter 10. The multimeter 10 conventionally measures the voltage ofthe test signal and takes the voltage measurement, which may be storedin the memory 54. After the voltage measurement is taken, the value canbe encoded in communication signals generated by the multimeter 10 andtransmitted to the multimeter test system 100 for comparison against theknown voltage value of the test voltage signal applied to themeasurement terminals 12. In another embodiment, the multimeter testsystem 100 transmits communication signals to the multimeter 100 throughthe measurement terminals 12 to invoke a self-evaluation routine withinthe multimeter 10 to test operability and functionality of themultimeter system. The results of the self-evaluation (i.e., pass, fail,type of failure) can be encoded in communication signals generated bythe multimeter 10 and transmitted to the multimeter test system 100 forevaluation.

In another embodiment, the DCMM 30 (FIG. 2) represents a multimetercalibration system 110, as shown in FIG. 5 b, coupled to the measurementterminals 12 for calibrating the multimeter 10. For example, aftercommunication between the calibration system 110 and the multimeter 10has been established and the multimeter 10 is placed into a calibrationmode, the calibration system 110 can apply known value test signals tothe measurement terminals 12 to be measured by the multimeter 10. Aftercompletion of the measurement, the multimeter 10 can determinemeasurement deviation between the known value and the measured value.The multimeter 10 then performs a calibration procedure to calibrateitself to correct for the measurement deviation.

In another embodiment, the DCMM 30 represents a multimeter softwareupgrade system 120, as shown in FIG. 5 c, coupled to the measurementterminals 12 for upgrading the software of the multimeter 10. Forexample, where a newer version of software for the multimeter 10 isavailable, the multimeter can be coupled to the software upgrade system120 through the measurement terminals 12. After communication betweenthe upgrade system 120 and the multimeter 10 is established, the upgradesystem 120 transmits communication signals to the measurement terminals12 of the multimeter 10 which include information for commanding themultimeter 10 to enter an upgrade mode. The software upgrade istransmitted in communication signals to the measurement terminals 12 aswell. The multimeter 10 receives the communication signals and installsthe software upgrade.

In another embodiment, the DCMM 30 represents a computer system 130, asshown in FIG. 5 d, coupled to the measurement terminals 12. The computersystem 130 can be optionally coupled to a network through networkconnection 132, which represents wired and wireless network connections.The network to which the computer system 130 is coupled can be alocal-area network, wide-area network, the Internet, or other networkover which the computer system 130 can communication with other computersystems. The computer system 130 can be used to communicate with themultimeter 10 for a variety of purposes. The computer system 130, forexample, can be programmed with failure analysis tools and communicateswith the multimeter for the purpose of determining a failure mode of themultimeter 10. In this example, after communication between the computersystem 130 and the multimeter 10 is established, the computer system 130can transmit communication signals to the multimeter 10 having varioustest routines or evaluation programs that are performed by themultimeter 10. Upon completion of a test, the multimeter 10 can generatecommunication signals including the results of the testing and transmitthe signals through the measurement terminals 12 to the computer system130. In other examples, the computer system 130 can be appropriatelyprogrammed to perform a portion or all of the multimeter testingperformed by a multimeter test system, such as that previously describedwith reference to FIG. 5 a. Similarly, the computer system 130 can beprogrammed to perform calibration or software upgrade of the multimeter10, as previously discussed with reference to FIGS. 5 b and 5 c. Moregenerally, a computer system 130 can be programmed to communicate withthe multimeter 10 through the measurement terminals 12, includingsending information to the multimeter 10 as well as receivinginformation from the multimeter 10.

In some embodiments, the multimeter 10, although including componentsfor communicating through the measurement terminals 12, can operate withconventional measurement probes. That is, the multimeter 10 operates andfunctions as a conventional multimeter when coupled to measurementprobes that do not include components for communication through themeasurement terminals 12. The difference being that the multimeter 10will not communicate an information to the measurement terminals 12 tothe conventional measurement probe.

In some embodiments of the invention, the multimeter can provide deviceinformation to the test system, calibration system, upgrade system, andcomputer system 130. For example, identification information (e.g.,serial number, manufacture date, location of manufacture, etc.), storedin the memory 54, can be encoded in communication signals andtransmitted by the multimeter 10 through the measurement terminals 12.Maintenance history stored in the memory 54 is another example of deviceinformation that can be provided to the different examples of DCMMs,such as last test date, calibration dates, software upgrade dates, andthe like. Upon completion of the testing, calibration, upgrade, ormaintenance, the DCMM transmits communication signals having informationfor updating the maintenance history stored in the memory 54.

In another embodiment, the DCMM 30 represents a measurement probe 140,as shown in FIG. 6, coupled to the measurement terminals 12 of themultimeter 10. Unlike conventional measurement probes, the measurementprobe 140 includes circuits and communication components forestablishing communication with the multimeter 10, generatingcommunication signals that are transmitted to the multimeter 10 in orderto provide it with information, and receiving communications signalsfrom the multimeter 10 and extracting information from the signals.

FIG. 7 illustrates a portion of the measurement probe 140 according toan embodiment of the present invention. The measurement probe 140includes a measurement sensor/source 150 that senses the characteristicto be measured and provides output signals according the measurement.The measurement sensor/source 150 can be conventional. The embodiment ofthe measurement probe 140 further includes a processor 152,communication component 168 and I/O communication circuit 164 coupled tothe probe terminals 170 for generating, providing, and receivingcommunication signals during communication with the multimeter 10. Inanother embodiment, the measurement probe 140 may further include aswitch circuit 172 controlled by the processor 152 selectively decouplethe measurement sensor/source from the probe terminal 170 whentransmitting or receiving communication signals from the multimeter 10.

In some embodiments, the communication signals can be alternately sentwith a measurement signal. In other embodiments, however, thecommunication signals is sent encoded in the measurement signal usingknown signal processing techniques.

The processor 152 determines when and what information should beprovided to the multimeter 10 in preparation for sending information tothe multimeter 10. The information is provided to the communicationcomponent 168 which generates communication signals having theinformation encoded for transmission. As with the I/O communicationcircuit 64 of the multimeter 10, the I/O communication circuit 164receives the communication signals from the communication component 168and generates output communication signals that are transmitted to themeasurement terminals 12 of the multimeter 10. On the receiving side,the I/O communication circuit 164 detects input communication signalsfrom the multimeter 10 and generates corresponding internalcommunication signals provided to the communication component 168. Thecommunication component 168 extracts information from the internalcommunication signals and provides the extracted information to theprocessor 152.

FIG. 8 illustrates communication from the measurement probe 140according to an embodiment of the present invention. The I/Ocommunication circuit 164 detects a query signal from the multimeter 10at step 180. As previously discussed, the multimeter 10 sends out aquery signal to establish communication with a DCMM, such as themeasurement probe 140. At step 182, the processor 152 determines whethera communication event has occurred. Generally, a communication event isan event that causes the measurement probe 140 to communicate with themultimeter 10. An example of a communication event is switching of ameasurement range of the measurement probe 140. In this particularexample, the measurement probe can send information to the multimeter 10to change the presentation of the measurement value on the display 22 sothat a user does not need to mentally convert the reading on the display22 to obtain the correct measurement value, such as with conventionalcurrent probes where the reading on the display is in the measurementunits of Volts, and the value needs to be mentally converted to thecorrect magnitude and correct measurement units.

In response to detecting a communication event, the processor 152prepares the information related to the communication event and theinformation is provided to the communication component 168 to generatecommunication signals including the relevant information at step 184.The communication signals are provided to the I/O communication circuit164, and at step 186, are transmitted to the measurement terminals 12 ofthe multimeter 10. As previously described, the multimeter 10 receivesthe communication signals, extracts the information, and performs thedesired action according to the extracted information. After thecommunication signals are provided to the multimeter 10 by themeasurement probe 140, the processor 152 returns to step 182 and waitsfor the occurrence of another communication event to repeat thecommunication process shown in FIG. 8.

In other embodiments, additional steps are included, such as having themultimeter 10 send communication signals to the measurement probe 140 toindicate acknowledgement of receiving the measurement probe'scommunication signals and confirming performance of the requestedaction.

In a particular example, the measurement probe 140 is a current probe.As known, current probes are connected to the measurement terminals of amultimeter and measure current in a conductor. Current probes typicallyconvert a measured current into a proportional voltage that is appliedto the measurement terminals of a multimeter. The proportional voltageis displayed on the multimeter in the measurement unit of Volts.Additionally, current probes typically have manually selectablemeasurement ranges to accommodate the measurement of a wider range ofcurrents. The measured value shown on the display of the multimeter,however, is shown on the same scale for the different current ranges,necessitating a user to convert the displayed value according to theselected measurement range on the current probe to obtain the actualcurrent measurement. As one can imagine, errors can be made indetermining the actual current value from the displayed value.

In an embodiment of the invention having a current probe connected tothe multimeter, the current probe can provide the multimeter withinformation to change the display value according to the measurementrange selected at the current probe. For example, after communicationbetween the current probe and the multimeter 10 have been established,as previously discussed, a processor in the current probe monitors thestatus for changes in the selected measurement range (i.e.,communication event). Upon detecting a change in the current measurementrange, for example, from a 20 A range to a 200 A range, the processorprepares information that is encoded in communication signals by thecommunication component that include information commanding themultimeter to change the display value according to the change. In theexample of changing from the 20 A range to the 200 A range (a factor of10×), the information in the communication signals includes commands forthe multimeter to shift a decimal point in the display one digit to theright to reflect the change in the measurement range.

In another embodiment of the invention, the communication signals canfurther include information to change the measurement unit displayed bythe multimeter. For example, upon connecting the current probe to themultimeter and establishing communication with the multimeter, theprocessor of the current probe can provide information encoded incommunication signals for commanding the multimeter to change fromdisplaying Volts measurement units to Ampere measurement units. In otherembodiments of the invention, the communication signals can provideinformation related to probe functionality and/or operation. Forexample, the probe can provide communication signals to the multimeterindicating whether the measured electrical characteristic is steadystate or alternating so that the multimeter can perform the appropriatecalculations and provide an accurate measurement.

It will be appreciated by those ordinarily skilled in the art that otherinformation can be communicated between a measurement probe and amultimeter other than that specifically described above. Consequently,embodiments of the invention should not be limited to the specificexamples previously described.

Other examples of measurement probes that may benefit from acommunication system according to an embodiment of the invention includethermocouple temperature probes, thermistor temperature probes, pressuresensors, circuit breaker locator probes, CO2 or CO probes, infraredprobes, relative humidity probes, probes for locating electricalconductors, and the like. For example, the multimeter can be controlledby communication signals from the probe to change the display to thecorrect measurement units and/or controlled to display visualinformation (e.g., graphics) for a user. Communication signals from theprobe can also provide information regarding probe configuration andother probe information, for example, probe status, probe functionality,and probe operability. Other types of information not expresslydescribed herein can be communicated between the probe and multimeter aswell without departing from the scope of the present invention

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A multimeter, comprising: measurement terminals; an input circuitcoupled to the measurement terminals and configured to receivemeasurement signals applied to the measurement terminals; aninput/output (I/O) communication circuit coupled to the measurementterminals to receive communication signals applied to the measurementterminals; a communication component coupled to the I/O communicationcircuit to receive the communication signals received by the I/Ocommunication circuit and configured to extract information from thecommunication signals; and a processor coupled to the input circuit andthe communication component, the processor configured to calculate ameasurement value from the measurement signals and further configured toperform an action in accordance with the extracted information.
 2. Themultimeter of claim 1 wherein the communication component is configuredto receive information from the processor and generate communicationsignals encoded with the information and is further configured toprovide the communication signals to the I/O communication circuit, theI/O communication circuit configured to provide the communicationsignals from the communication component to the measurement terminals.3. The multimeter of claim 2 wherein the communication component isconfigured to generate communication signals encoded with the digitalinformation.
 4. The multimeter of claim 1 wherein the I/O communicationcircuit is configured to receive communication signals having digitalinformation and the communication component is configured to extract thedigital information from the communication signals.
 5. A multimetercommunication system, comprising: a multimeter having measurementterminals and configured to receive measurement signals applied to themeasurement terminals and calculate a measurement value therefrom, themultimeter further configured to receive communication signals havinginformation encoded thereon applied to the measurement terminals andextract the information from the communication signals; and a devicecoupled to the measurement terminals of the multimeter and configured togenerate communication signals having the information encoded thereonand provide the same to the measurement terminals of the multimeter. 6.The multimeter communication system of claim 5 wherein the devicecomprises a multimeter software upgrade system configured to encode thesoftware upgrade on communication signals applied to the measurementterminals of the multimeter and wherein the multimeter is configured toreceive the communication signals applied to the measurement terminalsand extract the software upgrade encoded on the communication signals.7. The multimeter communication system of claim 5 wherein the devicecomprises a multimeter calibration system configured to generatecommunication signals having calibration information encoded thereon andfurther configured to apply the communication signals to the measurementterminals of the multimeter, and wherein the multimeter is configured toreceive the communication signals applied to the measurement terminalsand extract the calibration information encoded on the communicationsignals and further configured to perform calibration operationsaccording to the extracted calibration information.
 8. The multimetercommunication system of claim 5 wherein the multimeter is configured togenerate communications signals having information and transmit thecommunication signals to the device through the measurement terminalsand wherein the device is configured to receive the communicationsignals from the multimeter and extract information therefrom.
 9. Themultimeter communication system of claim 8 wherein the device comprisesa multimeter test system configured to apply test measurement signals tothe measurement terminals of the multimeter and further configured toreceive communication signals provided by the multimeter through themeasurement terminals and extract test information encoded on thecommunication signals and wherein the multimeter is configured to encodetest information related to the test measurement signal on thecommunication signals and provide the same to the multimeter test systemthrough the measurement terminals.
 10. The multimeter communicationsystem of claim 8 wherein the device comprises a computer systemconfigured to generate communication signals and apply the communicationsignals to the measurement terminals of the multimeter, the computersystem further configured to receive communication signals from themultimeter through the measurement terminals and obtain information fromthe communication signals.
 11. A multimeter measurement system,comprising: a multimeter having measurement terminals and configured toreceive measurement signals applied to the measurement terminals andcalculate a measurement value therefrom, the multimeter furtherconfigured to receive communication signals applied to the measurementterminals and extract information from the communication signals; and ameasurement probe coupled to the measurement terminals of the multimeterand configured to generate measurement signals in response to taking ameasurement and coupling the measurement signals to the measurementterminals of the multimeter.
 12. The multimeter measurement system ofclaim 11 wherein the measurement probe is configured to generatecommunication signals representing information and transmit thecommunication signals to multimeter via the measurement terminals. 13.The multimeter measurement system of claim 12 wherein the measurementprobe comprises a measurement probe having a selectable measurementrange and the measurement probe is configured to generate thecommunication signals in response to changes in the selection of themeasurement range.
 14. The multimeter measurement system of claim 13wherein the multimeter includes a display and the multimeter isconfigured to receive the communication signals from the measurementprobe through the measurement terminals, obtain the information from thecommunication signals, and modify display of a measurement value on thedisplay.
 15. The multimeter measurement system of claim 12 wherein themeasurement probe is configured to generate communication signalsrepresenting probe identification information and transmit thecommunication signals to the multimeter via the measurement terminals.16. The multimeter measurement system of claim 11 wherein themeasurement probe comprises at least one of a thermocouple temperatureprobe, thermistor temperature probe, pressure sensor probe, circuitbreaker locator probe, CO_(X) probe, infrared probe, relative humidityprobe, and a probe for locating electrical conductors.
 17. A method forcommunicating with a multimeter, comprising: generating signalsrepresenting information to be extracted by the multimeter; transmittingthe signals to measurement terminals of the multimeter; receiving thesignals at the measurement terminals; and extracting the informationfrom the signals.
 18. The method of claim 17, further comprisingcoupling measurement signals to the measurement terminals of themultimeter and calculating a measurement value from the measurementsignal.
 19. The method of claim 18 wherein transmitting the signals tothe measurement terminals of the multimeter and coupling measurementsignals to the measurement terminals are concurrent.
 20. The method ofclaim 17, further comprising generating signals representing informationto be transmitted by the multimeter from the measurement terminals. 21.The method of claim 20 wherein generating signals representinginformation to be transmitted by the multimeter from the measurementterminals comprises generating signals representing at least one of atest measurement value, multimeter identification information,multimeter maintenance information, query information, and self-testinformation.
 22. The method of claim 17 wherein generating signalsrepresenting information to be extracted by the multimeter comprisesencoding digital information on signals to be extracted by themultimeter.
 23. The method of claim 17 wherein generating signalsrepresenting information to be extracted by the multimeter comprisesgenerating signals representing at least one of calibration information,software upgrade information, and measurement range information.
 24. Amethod for configuring operation of a multimeter, comprising: generatingcommunication signals encoded with multimeter configuration informationto be extracted by the multimeter; transmitting the communicationsignals to measurement terminals of the multimeter; receiving thecommunication signals at the measurement terminals; extracting themultimeter configuration information from the communication signals; andconfiguring the multimeter according to the extracted multimeterconfiguration information.
 25. The method of claim 24 wherein generatingcommunication signals encoded with multimeter configuration informationcomprises generating communication signals encoded with measurementrange information and wherein configuring the multimeter according tothe extracted multimeter configuration information comprises configuringdisplay of measurement values by the multimeter.